The invention relates generally to forensic analysis, and, more specifically, to repair of damaged nucleic acid sequences.
In criminal investigations, investigators often look for physical evidence left behind at the scene of a crime to link a suspect to the crime. For example, physical evidence has traditionally included fingerprints, hairs, fibers, and so forth. A modern forensic analysis of physical evidence may include analysis of evidence, such as blood or other bodily fluids, which contains deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) specimens. Forensic laboratories analyze DNA and/or RNA samples in an attempt to determine the identity of the person to whom the sample belongs. For example, in criminal forensics, a subject may leave blood or other evidence containing DNA at the scene of the crime. By determining from whom the DNA evidence came, the government can use such evidence in court to prosecute a suspect.
DNA analysis performed at forensic laboratories may be hampered by DNA samples that have been exposed to uncontrolled environmental conditions. Environmentally damaged samples may contain shortened DNA fragments (i.e., double-stranded breaks in the DNA), which are refractive to standard analysis methods, or may contain somewhat intact DNA with single-stranded nicks and lesions. Some examples of damaging exposure include acid and heat exposure, which leads to missing bases and/or apurinic and apyrimidinic sites (AP sites); ionizing radiation and electrophilic agents, including alkylating agents, which modify bases or the sugar backbone; oxidative damage, which leads to altered bases; and UV irradiation, which produces cyclobutane dimers. In the event of such damage, the DNA sample often cannot be analyzed effectively and thus cannot be used as evidence in criminal prosecutions.